Dating the Earth: Amino Acid Racemization

I have taken part in many discussions on internet discussion boards with pastors and lay Christians concerning science and the age of the earth. Here is comment made in just such a discussion more than 10 years ago:

>As I understand it, the “old earth” position bases its beliefs on
>an unknowable fact. It is assumed that the earth is billions of years old.
>The instruments (radiometers, C-14, etc.) that measure the isotopes that
>give these supposed billions of years ARE calibrated on those assumptions.
>Yes, we can know the half life of carbon and the other properties of
>isotopes that can help us determine the age of these elements but it is
>assumed that these elements are already billions of years old.

This is a very common claim among young earth creationists and to the lay Christian sounds like common sense. Aren’t dating mechanisms used to test the validity of other testing mechanisms? Well to some extent maybe but it reveals a very simplistic understanding of dating techniques and of science itself. He is one example I have offered in the past to this exact comment above:

That the earth is assumed to be billions of years old cannot be considered an a-priori assumption given that this this age for the earth has only been estimated in the last 100 years. These dates are derived by measuring decay rates and extrapolating back in time which is very different than calibrating it to come out that way a priori. Now it could be that one may wish to object to the particular use of an uniformitarian assumption that is part of such an extrapolation but that would be a different complaint. Furthermore, to object to the constancy of radiometric decay would not go far in explaining why in the vast majority of cases different dating methods that work in operate in different ways under different physical assumptions result in ages that are for the most part highly convergent.

Let us take a lesser known form of dating as an example. This is a very “messy” type of dating which, I admit, is not very accurate but it is very different than most. I won’t pretend this is the strongest argument for an apparently old earth but it is fairly simple to understand and illustrates a point. This method has to do with the chirality of molecules. Amino acids that contain a single chiral carbon can exist in two stereoisomeric forms, which are mirror images of one another; one of these rotates polarized light to the left (L-form) the other to the right (D-form). The proteins of all living things contain single chiral carbons that are of the L-form rather than D-form. Upon death which is a condition that lacks biophysical maintenance or replacement of parts of an organism the organic molecules (amino acids) are slowly converted (decayed) to D-form amino acids until a 1:1 mixture of the two is attained (at this point equal numbers of D-form and L-form are being converted back and forth). This process takes a long time and proceeds at different rates for different amino acids and depends on humidity, temperature and some other physical constraints which is why I say it is a “messy” type of dating. Organic remains of known age (say 2500 or less) determined by other methods that everyone would agree are quite reliable are nowhere near a 1:1 ratio exhibiting only a tiny amount of “racemization” (or L- to D-conversion). Partially fossilized and other “ancient” things with organic remains (that all would be interpreted as post-Flood by young earth creationists) often exhibit ratios of 1:1 or near 1:1. It is estimated that even under optimal conditions (the most extreme conditions that would allow the fastest rate of racemization given all the laws governing chemical bond conversions) that it would take at least 150,000 years for any organic matter that dies now to achieve a 1:1 ratio. Objects of known ages of 1000-2000 years old can be accurately dated etc.. Obviously if an object is at or near equilibrium, the know rates of decay extrapolated backwards by conventional chemistry would lead a person to conclude the object is old. So if remains of organic material are the remains of things that lived within the past 10,000 years what are the possible explanations within a young earth cosmology?

1) The racemization rates were much faster in the past than in the present so the extrapolation back is wrong. Could be, but this again requires that one postulates that chemistry worked in a fundamentally different way in the past. An added complication is that many objects found in caves such as remains of animals or pollen sediments from 10-100 feet below the ground exhibit ratios near equilibrium suggesting a very old age but these bones or pollen are interpreted by all scientific creationists as being POST-Flood thus one cannot use an explanation that the days before the Flood were somehow so different. But rather one must argue that the laws of physics have radically changed even during the period after the flood. Is there precedent for this in the Scriptures? Does an understanding of general revelation allow for large changes in the basic laws of chemistry and physics in the recent past? Maybe it does but there are some other interesting complications if one takes this point of view.

2) Another possible explanation is that living things in the past didn’t make and incorporate sugars in the same ratios. This might be tempting but there are several problems. a) If this was the case then it would be difficult to relate to our ancestors in any physical sense. Their bodies must have worked in a fundamentally different way even long after the Flood. This would be akin to saying that Adam didn’t have DNA, that’s how basic this is to living things. b) We have objects going back 4000 years of know ages that ALL show that living things made and used one form (the L-form) and not the other. What does one do with those things that based on OTHER methods such as C14 that suggest an age of 40,000 years or more and have amino acid ratios of 1:1? Is this just some incredible coincidence that something that C14 dating says is 40,000 years old has amino acid ratio much closer to 1:1? What do these have to do with each other? How would some sort of explanation for higher C14 ratios in the past have anything to do with racemization rates? The results from these two analyses should never really be correlated. Why can the two dating methods be used very efficiently to date a ancient text or something else that everyone agrees what the age of it is before it’s even dated?

3) I suppose one could argue that chemist just really don’t know anything about chemical bonds and so racemization of amino acids may operate in ways that are very different than any believes. If this is the case just throw your chemistry book out the window because you might as well stop believing that water is composed of two hydrogen atoms and an oxygen atom. Fairly basic chemistry and math will lead one very quickly to the conclusion that any remains with a 1:1 ratio is most easily interpreted as being 10,000+ years old. As I said in another post, that doesn’t mean we always must accept that simplest explanation. On the other hand, how is this a case where the scientist has calibrated the instrument to give an old age? What if one calibrated the measuring device (do-hickey that measure the ratios of molecules) to say that a 1:1 ratio meant the object was no more than 6000 years old, as young earth advocate suggests, what would happen to the other results? Well, every object one measured would certainly be assigned a different age than it had been before but now an object with say a 1.2:1 ratio instead of being assigned an age of 1500 years old would only be say 75 years old. What if one knew the object was 1500 years old (it is an autographed copy of a book by someone from the year 500) wouldn’t one say there was something wrong. The same thing is going to happen with C14 data. One would have to assume that the relationship wasn’t linear with time and that would require a change in many if not all of the physical constants of the universe. Where would ones baseline for calibration be: Creation or the Flood? Please not that all the coal and other carbon sources in the fossil record have ratios of 1:1 suggesting it has been completely racemizated.

Here again, the language used to describe the presuppositions of radiometric dating and the errors with it, are simplistic arguments meant to suggest that radiometric dating is just a matter of a priori beliefs and that without the assumption of billions of years the whole system would fall. This idea has been soundly and routinely criticized by other Christian scientists.